The 'last' word in hosting that should ever be spoken (or printed) impulsively is ~Refund~ by a host. Access the situation calmly, the logic or absurdity of the situation, and then maybe a refund applies in true fairness. We all been 'guilty' of this impulse to be kind, then we learn. 🙂
In this particular case, they want a refund without having made the slightest effort to be accomodating nor fair to you. Let Airbnb handle them. I am not a fan of calling Airbnb readily, but @Amy38's suggestion may be apropo in this case, to give Airbnb a heads up on the possible 'scam'.
Good luck.